Messing around with it for a minute it seems it's a modified base64 (+ and / are replaced by - and _) with a space every 56 characters. I couldn't get any permutation where a-z, A-Z, 0-9, and -_/_- were consistent so it's either encrypted or one of 1,268,869,321,858,841,641,034,33,389,335,161,480,802,865,516,174,545,192,198,801,894,375,214,704,230,400,000,000,000,000 permutations of the encoding alphabet (or I messed up the decoding).